The molecular basis of the growth inhibition observed in the human lymphoblastoid cell line Daudi treated with human fibrobast interferon will be examined. Experiments will determine whether the inhibition of cell proliferation is caused by a defect in RNA or protein synthesis. If these are found to be defective, an analysis of the RNA sythesized and of initiation factors necessary for active protein synthesis will be undertaken. It is hoped that these experiments will allow us to explain the antiproliferative effect of interferon observed by several investigators but not yet accounted for at the molecular level. Experiments with other cell lines will then extend our knowledge about the inhibitory properties of interferon.